1. Field of the Invention
The present invention relates to a discriminating method of an optical disc device for ascertaining a loaded optical disc, and more particularly relates to a method for discriminating the format of a R-type and ROM-type medium for the optical disc device.
2. Description of the Prior Art
The conventional procedure for reading data recorded on an optical disc includes the following steps. Firstly, referring to FIG. 1, a light beam radiated from a light source 101 is guided and reflected by a beam splitter 107 and a mirror 109, and then penetrates a lens 111 to project onto the loaded optical disc 103. Thereafter, a reflected light beam, which sequentially penetrating the lens 111, reflected by the mirror 109, and penetrating the beam splitter 107, is finally detected by a photodetector 105 and then converted into several detection signals. In this so-called “Disc ID” step of conventional approach, the structure of the loaded optical disc could be identified as a CD or DVD, or as single-layer or a dual-layer according to a focusing error (FE) signal derived from the detection signals. In this regard, referring to FIG. 2A and FIG. 2B, if there is only one s-curve such as the waveform 201 of FIG. 2A shown in the detected focusing error signal, the structure of the loaded optical disc 103 could be identified as a single-layer. On the other hand, the loaded optical disc 103 could be identified as a dual-layer structure if there are two s-curves as the waveform 203 of FIG. 2B being detected in the focusing error signal. On the other hand, the optical disc device might recognize the loaded disc as a CD or DVD by means of the waveforms of s-curves since the distance between the reflection layer and data layer of CD is usually larger than that of the DVD. However, the optical disc device does not recognize the loaded one is a R-type or ROM-type medium only by using s-curves. Thereafter, the optical disc device performs a focus-on procedure under a close-loop control, while all parameters for reading disc (e.g., equalizing parameter) are adjusted according to requirements of the currently loaded disc during a calibrating procedure. A default disc structure, e.g. a DVD-R or a DVD-ROM, is assumed for the currently loaded optical disc at the beginning of the calibrating procedure because the actual disc format is still unknown until the lead-in area of the loaded one is correctly accessed during the calibrating procedure. Thereafter, the optical disc device may fetch the recorded data from the loaded optical disc after recognizing actual disc format. It is obvious a time-cost way for the conventional calibrating procedure to fetch the recorded data correctly since the actual format of the loaded optical disc cannot be recognized immediately.
A discriminating method is necessary for the optical disc device to ascertain the format of the loaded optical disc quickly, and more particularly to distinguishing the format between the R-type and ROM-type medium.